Much evidence indicates that the retina largely regulates eye growth and the development of refractive errors, but the identity of both the cellular pathways and the molecular components of the signaling cascade by which the retina controls scleral growth in vivo are poorly understood. We propose to investigate mRNA expression by individual retinal pigment epithelial (RPE) cells to address local retina-to-sclera signaling in eye growth control because RPE cells form the intervening barrier layer between the sensory retina and the choroid/sclera and, based on available data, could locally mediate the retinal influences on refractive development. We shall study gene expression in individual RPE cells selected from different fundus regions in two well-established eye growth models in the chick by applying microarray profiling to amplified antisense-RNA (aRNA) prepared from the mRNA of these cells. Combining an interdisciplinary research team and University of Pennsylvania core facilities, we propose the following inter-related Specific Aims: 1) prepare aRNA from the mRNA of individual RPE cells located at different fundus regions in eye growth models; 2) complete and then utilize high density chick RPE/retinal microarrays to profile aRNA from RPE cells; 3) adapt informatics approaches for analysis of gene expression by individual RPE cells; and 4) validate the cellular gene expression profiles. By identifying mRNA expression patterns according to RPE cell location, we anticipate that the results will further implicate RPE cells in the growth regulatory process and provide novel molecular and spatial information about the local signaling from retina to sclera in refractive development. Further, demonstrating the feasibility and utility of single cell mRNA profiling for refractive research could substantially advance the available techniques and provide the foundation for future cell and molecular studies in the area. We believe this program will lead to improved understanding of the etiology of refractive errors and ultimately to effective approaches to arrest myopia in children.